Exemplary embodiments described herein are directed to the problem of data processing as it relates to monitoring the time-varying nature of a data item. In some situations, changes in a data item may not be directly recorded in a structure accessible to a system responsible for maintaining records relating to the data item. Conventionally, it is very difficult to determine the status of the data item from the information available, and systems are often left to estimate, at a high level of granularity, very general properties of the data item (e.g., the value of the data item may be estimated only very roughly, or only at widely-spaced intervals).
The problem of inferring values for the data items in the presence of limited information can be further complicated when some data items can serve as substitutes for others. For example, an event that changes the value of a data item in a particular class of data items may affect only one of the items in that class. It can be difficult to properly address the value of a given data item when the values of that data item are not directly observed and the data item is fungible with another data item.